In polyurethane foam manufacturing, surfactants are needed to stabilize the foam until the product-forming chemical reaction is sufficiently complete so that the foam is self-supporting and does not suffer objectionable collapse.
Silicone polyether surfactants for polyurethane foam manufacture typically are materials having siloxane backbones and polyether pendant groups. They are of two types, nonhydrolyzable and hydrolyzable. The nonhydrolyzable surfactants, in which the polyether pendant groups are attached to the siloxane backbone by Si--C bonds, are generally believed to have high potency but produce "tight" foams with poor breathability. Hydrolyzable surfactants, in which the polyether pendant groups are attached to the siloxane backbone by Si-bonds, are generally believed to have poor potency but offer good processing characteristics, and produce foams with good breathability.
Flexible slabstock polyurethane foam is made by two different processes: the continuous process or the discontinuous process. In the continuous process, the raw materials are fed continuously through a mixer and deposited onto a moving conveyor. Along the conveyor, the foam rises, cures and is cut into blocks of foam. In the discontinuous process, the raw materials are mixed in a stirred tank and poured into a large box.
All foam applications require that the final foam be free of "splits". Splits are ruptures between the foam cell struts which weaken the structural integrity of the foam. Splits are thought to be caused by weakened struts characterized by altered non-uniform cell structure and sizes.
In the continuous process, the surfactant is thought to stabilize the gas nucleation sites, to stabilize the rising foam, and to regulate the cell structure of the foam. Splits are generally though to occur when a foam is under stabilized or over stabilized by either the surfactant or the formation of the polymer network. An effective surfactant used in the continuous process, theoretically stabilizes the foam without causing over stabilization.
Typically, a discontinous process surfactant possesses good emulsification properties because mechanical mixing in a discontinuous process is generally not as good as in the continuous process. It is believed that splits occur in a discontinuous process when the raw materials are not compatibilized properly. We have shown that one source of splits is due to silicone polyether surfactant structure used in the production of the foam. For example, a commercially produced silicone polyether produces splits in discontinuous processes, but not in continuous processes.
Further, the specific polyol chosen for either process can require a surfactant with improved emulsification properties. For example, polyol's made entirely of propylene oxide have a low water solubility which requires better emulsification and therefor it is thought that a surfactant that emulsifies better is needed. Also, as chlorinated solvents are being eliminated, water levels in newer formulations are increasing. Therefore, ethylene oxide/propylene oxide polyol formulations require better emulsifiers as water levels increase.
The silicone polyether surfactants of this invention are particularly useful from the preparation of a type of urethane foam manufactured in a discontinuous process (Box-Foaming) and the continuous process. Less-developed countries use a commerical box foam process. The term "box foam" comes from the shape of the container used in the manufacture. The box is constructed so that the sides are hinged to the bottom so that the final foam can be removed from the mold easily. The foam is then cut into various sizes for a variety of uses. An example of a typical discontinuous commercial Box-Foaming machine is described in Flexible Polyurethane, Ron Herrington, Kathy Hock, Flexible Polyurethane Foams, copyright 1991, by The Dow Chemical Company. 5.11-5.17 which is hereafter incorporated by reference. Examples of silicone surfactants are described in U.S. Pat. No. 4,147,847. This patent describes certain siloxane-oxyalkylene copolymer silicone surfactants which reduces the occurance of splits in polyurethane compositions. Other surfactants having cyclic siloxane pendant groups as well as polyether pendants, are described in U.S. Pat. No. 4,855,379.
U.S. Pat. No. 3,979,419 to Prokai et al. teaches organosilicone compositions which comprise polysiloxane-polyoxyalkylene copolymers containing monofunctional siloxy units and difunctional siloxy units, an average of between about 2 and about 20 silicon-bonded cyano-bearing ether groups for every two moles of monofunctional units, said cyano-bearing ether groups having the formula, --(O).sub.q R'OR"CN, wherein q is zero or one, R' is bivalent alkylene of 3 to 8 carbon atoms and R" is bivalent alkylene of 2 to 4 carbon atoms, and an average of between about 2 and about 30 silicon-bonded, organic-capped polyoxyalkylene blocks for every two moles of monofunctional units, at least 75 weight percent of the polyoxyalkylene content of said copolymers being constituted of oxyethylene units, said monofunctional units having at least two alkyls bonded to the respective silicon atoms thereof and the difunctional units having at least one alkyl bonded to the respective silicon atoms thereof, the remaining organic group bonded to silicon of the respective monofunctional and difunctional siloxy units being alkyl, said cyano-bearing ether group or said polyoxyalkylene block. The polymers of the present invention, however are structurally different compounds from those described in Prokai, because Prokai teaches cyano-bearing ether groups whereas the present invention does not.
U.S. Pat. No. 3,979,420 to Prokai et al. teaches organosilicone compositions which comprise polysiloxane-polyoxyalkylene copolymers containing monofunctional siloxy units (M.sub.o) and, for every two moles of M.sub.o, an average of between about 10 and 200 difunctional dialkylsiloxy units, and average of between about 2 and about 100 silicon-bonded cyano-bearing ether groups (Q) having the formula, --(O).sub.q R'OR"CN, wherein q is zero or one, R' is bivalent alkylene of 3 to 8 carbon atoms and R" is bivalent alkylene of 2 to 4 carbon atoms, and an average of between about 2 and about 30 silicon-bonded, organic-capped polyoxyalkylene blocks (E), the polyoxyalkylene content of said copolymers being constituted of between about 20 and about 65 weight percent of oxyethylene units, said M.sub.o units having at least two alkyls bonded to the respective silicon atoms thereof, the remaining organic group of M.sub.o being alkyl, 0 or E, said copolymers also containing difunctional monoalkylsiloxy units the remaining organic group bonded to the respective silicon atoms thereof being Q or E. The polymers of the present invention are structurally different from those taught in Prokai, because Prokai teaches CN bearing compounds and the present invention does not.
U.S. Pat. No. 3,980,688 to Litteral et al teaches polyoxyalkylene polyether admixtures and polysiloxane-polyoxyalkylene block copolymers, a solventless process for producing said copolymers using said admixtures, a process for producing flexible polyether polyurethane foam using said copolymers as foam stabilizers and the foam produced thereby. Litteral, however, teaches cyclic structures as a part of the composition whereas the present invention does not.
U.S. Pat. No. 4,016,000 to Prokai et al teaches organosilicone polymers are provided which comprise polysiloxane-polyoxyalkylene block copolymers wherein the polysiloxane blocks are trialkylsiloxyend-blocked and contain reoccurring difunctional dialkylsiloxy monomeric units in combination with reoccurring difunctional cyanoalkyl-alkylsiloxy or cyanoalkoxyalkylsiloxy monomeric units, the mol ratio of the dialkylsiloxy units to the cyano-substituted siloxy units being about 10-200:3-100, and wherein the polysiloxane polyoxyalkylene blocks are joined through an Si--C or an Si--O--C linkage, and from about 20 to about 65 weight percent of the oxyalkylene units of the polyoxyalkylene blocks are constituted of oxyethylene units. The block copolymers of the invention are effective stabilizers of flexible polyether polyolbased polyurethane foams and offer particular advantage in the formation of flame-retarded foams. Also provided is a particular class of cyano-substituted polyalkylsiloxane hydrides which are useful in the preparation of the aforesaid block copolymers. The present invention does not teach the use of cyan-substituted structures.
U.S. Pat. No. 4,018,723 to Kanner et al. teaches organosilicone compositions are provided which comprise polysiloxane-polyoxyalkylene copolymers containing monofunctional siloxy units (M.sub.o) and difunctional siloxy units (D.sub.o), an average of between about 2 and 100 silicon-bonded morpholino-bearing groups (Q) for every two moles of M.sub.o and an average of between 2 and about 30 silicon-bonded, organic-capped polyoxyalkylene blocks (E) for every two moles of M.sub.o, the monofunctional units encompassed by M.sub.o having at least two alkyls bonded to the respective silicon atoms thereof and the difunctional units encompassed by D.sub.o having at least one alkyl bonded to the respective silicon atoms thereof, the remaining organic group bonded to silicon of said monofunctional and difunctional siloxy units being alkyl, 0 or E.
U.S. Pat. No. 4,045,381 to Prokai et al. teaches cyano-modified polysiloxane-polyoxyalkylene block copolymers that contain a trifunctional RSiO.sub.3/2 siloxy unit, as well as, a process for producing flexible polyether urethane foam wherein said copolymers are employed as the foam stabilizing component. The present invention does not teach cyano-modified structures.
U.S. Pat. No. 4,107,068 to Prokai et al. teaches acrylonitrile-capped polyoxyalkylene compounds; siloxane polymers modified with the corresponding radicals of said compounds; solvent compositions containing said siloxane polymers; a process for producing polyurethane foam using said siloxane polymers as the foam stabilizer; and the foam produced from said process. The present invention does not teach anylonitrile-modified compounds.
U.S. Pat. No. 4,110,271 to Kanner et al. teaches the formation of polyurethane foam including flame-retarded foam is provided employing, as the surfactant component of the foam formulation, a particular class of sulfolanyloxyalkyl-substituted polysiloxane-polyoxyalkylene polymers. The polymers comprise chemically combined monofunctional siloxy units (M.sub.o) and difunctional siloxy units (D.sub.o) and, for every two moles of M.sub.o, an average of from about 2 to about 100 silicon-bonded sulfolanyloxyalkyl groups (Q) and an average of from about 2 to about 30 silicon-bonded polyoxyalkylene blocks (E). The M.sub.o units have at least two alkyls bonded to the respective silicon atoms thereof and the D.sub.o units have at least one alkyl bonded to the respective silicon atoms thereof, the remaining group bonded to silicon of said M.sub.o and D.sub.o units being alkyl, W or E. When the polyol reactant of the foam formulation is a polyether polyol, the polymers contain from 10 to 200 dialkylsiloxy units and from 2 to 100 Q groups, and the polyoxyalkylene content of E is constituted o from 20 to 75 weight percent oxyethlene. When the polyol reactant is a polyester polyol, the polymers contain zero or up to 20 dialkylsiloxy units and from 2 to 20 Q groups, and the polyoxyalkylene content of E is constituted of at least 75 weight percent oxyethylene. The present invention does not teach the us of sulfonanes.
U.S. Pat. No. 4,242,466 to Schilling, Jr. et al. teaches organic ethers including polyethers having two CH.sub.2 .dbd.C(R)CH.sub.2 -end groups per molecule wherein R is a monovalent hydrocarbon group are reacted with organohydrosiloxanes under hydrosilation reaction conditions in the presence of a platinum catalyst preferably a neutral platinum catalyst, to form very useful nonhydrolyzable siloxane block copolymers. Novel nonhydrolyzable linear block copolymers substantially free of silicon-bonded hydrogen are obtained with linear dihydropolyorganosiloxane reactants and linear ethers or polyethers.
U.S. Pat. No. 4,331,555 to Baskent et al. teaches a process for manufacturing low density flexible polyester polyurethane foam utilizing as a foam stabilizer selected low molecular weight (e.g., 400 to 1500) organosiloxane compositions containing monomeric units A, B and C wherein A is monofunctional trimethylsiloxy unit [(CH.sub.3).sub.3 SiO.sub.1/2], B is a difunctional dimethylsiloxy unit [(CH.sub.3).sub.2 SiO.sub.2/2 ] and C is a difunctional organomethylsiloxy unit [R(CH.sub.3)SiO.sub.2/2 ] where R is a cyano-, ether-, hydroxy-or phenyl-organo modifying moiety, and in which the unit ratio of B to C in each organosiloxane composition is from 1 to 4 inclusive; solutions of such organosiloxane compositions; and the foams derived from such process. The surfactants taught in Baskent, however, have a D/D' ratio of 6.7 to 13, whereas the D/D' ratio of the present invention is 14-18.
U.S. Pat. No. 4,367,291 to Baskent et al. teaches combustibility properties of flexible polyurethane foams made with flame retardant additives are increased by incorporating into the foam-forming reaction mixture a combination of certain flame retardant surfactants and certain low molecular weight polyols. The surfactants taught therein teach a D/D' ratio much smaller than that of the present invention.
U.S. Pat. Nos. 4,814,409 and 4,855,329 to Blevins, II et al. teaches the present invention provides certain polysiloxanepolyoxyalkylene compositions and their use as stabilizers in the manufacture of polyether polyurethane foam. More particularly, the present invention provides such compositions, which have a polysiloxane chain substituted with at least two types of polyoxyalkylene polymers as pendants from the silicon atoms of the polysiloxane.
The polysiloxane chain is linear or branched and can have average molecular weights of up to 30,000 or higher, excluding the weight of the polyoxyalkylene polymers.
The distinctive feature of these compositions is the specific selection of polyoxyalkylene polymers. Preferably the polyoxyalkylene polymer pendants are provided as at least three different polyoxyalkylene polymers. One of these polyoxyalkylene polymers is composed of only oxypropylene units. This polyoxypropylene has an average molecular weight from about 130 to about 1200 excluding link and endcap. The other polyoxyalkylene polymers are composed of both oxyethylene and oxypropylene units.
The present invention differs structurally from the two previously cited Blevins patents because the present invention has only a single type of pendant.
U.S. Pat. No. 4,855,379 to Budnik et al. teaches novel siloxane-polyether polymers are provided containing cyclic siloxanes which are useful in silicone surfactants for foam polyurethane foam applications. The novel polymers are prepared by reacting a polyhydridosiloxane polymer with a cyclic polysiloxane containing a vinyl group and with an allyl started polyoxyalkylene polymer in the presence of a platinum catalyst. The resulting polymeric products are highly potent and impart flat breathability profiles to foams when used as surfactants in their preparation.
U.S. Pat. No. 5,145,879 to Budnik et al. teaches silicone surfactants having a siloxane backbone and a mixture of high and low atomic mass oxyalkylene pendant groups, these polyether pendants having average atom mass is of 1500-6000 and 300-750 respectively. The surfactants of the invention operate in polyurethane foam compositions to provide stable foams over a range of surfactant concentrations while still producing product foams having relatively constant breathability. Also disclosed and claimed are polyurethane foam compositions which include the surfactants, a method of making polyurethane foam using the surfactants, and polyurethane foam made by the method. The present invention teaches a composition having only a single pendant group.
It would be desirable to have nonhydrolyzable silicone surfactants which have high efficiency, and offer good processing characteristics, such as good emulsification of TDI/H.sub.2 O, good water solubility without providing foam splits. Such surfactants are the subject of the present application.